Not sure if this is a story about falling down a rabbit hole, or one about how my brain will randomly make connections then bug me till I follow the breadcrumbs.

I was reading about beneficiation of claystone in a lithium extraction train when I decided I needed a break, saw that I had a LinkedIn notification, and checked to see what slop someone sent me.

And it was not slop but spam about being part of some company’s board, but as always I like to scroll before I close LinkedIn, and found a post about an EV that caught fire in a parking garage.

The top comment was from an actual Tesla employee whose job is dealing with fire safety, and she wondered if there was a problem with the sprinklers.

Predictably, this drew out all the lurkers with impressive titles who probably just harass actual engineers while pretending to be one, replying about the use of water on an EV fire.

For those who don’t know, the National Fire Protection Association (NFPA) recommends using water to put out an EV fire.

Anyways, I pulled a link of a UL report, the same one I linked in another note, and used it as a polite way to show one particular offensive participant of the conversation how he was wrong. But while I was looking up a section in that, a word caught my eye: smoldering.

That word for some reason caused another report that I had read about headlines and lithium-ion recycling to pop back into my head, specifically a section about black mass and dust explosions.

The EPA has 4 hazard codes that they apply to waste because they typically exhibit one of the four regulatory characteristics of hazardous waste

Ignitable Waste
Corrosive Waste
Reactive Waste
Toxicity Characteristic Waste

Black mass is classified as hazardous waste even though it is no longer considered a battery because it is ignitable and reactive and in some states they also include Toxicity due to the metals it can contain, but the common thinking, and the one I see in reports and studies, is because it is explosive due to being a fine dust.

Black mass is often referred to as a powder, but it can also be described as a fine dust one company even calls it a sand. This means it is made up of small particles of different materials, ranging from cathode material and actual foils to graphite. While it may seem counterintuitive, the smaller the particle, the more surface area oxygen has to wrap around. Once that dust is exposed to a high enough temperature, an explosion occurs.

For some reason, however, the word smoldering was stuck in my head like an earwig, and while I was not sure why, I knew it had to do with black mass and not the EV.

So I did a Google search for smoldering and black mass and wouldn’t you know it, I found this: Smoldering fire and explosion hazards of black mass in the lithium-ion battery recycling industry.

While black mass can technically be categorized as a dust, a dust explosion from ignition is not as prevalent as other studies have suggested. I am not surprised by this, since I am still seeing studies that include the 5% recycling myth.

The preliminary results show that the smoldering fire hazard is high, while the dust explosion hazard is low for representative black mass samples. Moreover, the safety concern of flammable gases (e.g., H₂ and NH₃) and/or volatiles released by the bulk black mass samples in enclosures cannot be ignored, especially when moisture and/or water is present. This raises another practical question: Can a sprinkler system be used for smoldering fire suppression of black mass?

A lower quality black mass can contain leftover chemicals from the breakdown of the electrolytes, and if the aluminum percentage is high enough, which in low quality black mass can be rather high along with copper, that aluminum could react to moisture, and this reaction can generate enough heat that, along with the leftover electrolyte chemicals, can create smoldering super sacks of black mass.

While there is a present and on going concern about explosions and a conflagration-style event, recent studies are showing that a slow, smoldering of the black mass that can creep undetected from one super sack to the next may be the main cause of concern. This heat can eventually build up enough to catch surrounding materials on fire. The less efficient a black mass production platform is, the higher the danger of storing black mass can be.

The negatives of high levels of aluminum in black mass are well documented. During leaching, aluminum can trap transition metals in the solid residue, preventing them from dissolving into solution. This cuts recovery rates and drives up operating costs, and is why companies are devloping and deploying far more efficient front ends to their recycling platforms, not only for cost-saving measures but also as can be seen from that report the added benefit of creating a safer intermediate.

I was once asked for a list of research materials by someone who wanted to learn about lithium-ion recycling. My response was to Google something you want to understand, read about it, and I can guarantee before you finish that paper you will discover another topic you will want to understand.

Before you know it, it’s seven years later and you are still learning something new.

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DISCLAIMER: This article should not be construed as an offering of investment advice, nor should any statements (by the author or by other persons and/or entities that the author has included) in this article be taken as investment advice or recommendations of any investment strategy. The information in this article is for educational purposes only. The author did not receive compensation, from any of the companies and or persons mentioned to be included in the article.

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